Code Protection (CP) technologies encompass a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals as a means of controlling the use of digital content and devices. CP technologies include technologies that inhibit uses of digital content that are not desired or intended by the content provider.
CP technologies seek to provide control of digital content or devices to a content provider or device seller after it has been purchased by a consumer. As it relates to digital content, such control can include preventing access to content, preventing content copying and preventing the conversion of content to other formats. As it relates to devices, such control can include restricting the hardware and software that can be used with a device.
Some conventional CP technologies are susceptible to specific types of attack. For example, software based CP technologies can be susceptible to attacks that are based on information that is contained by the software itself because the software can include information that can enable the decryption of content (e.g., decryption keys). Consequently, an attacker may be able to extract this information and decrypt and copy the content directly, and thereby bypass the restrictions imposed by the CP system
Hardware based CP technologies have susceptibilities as well. Some of these technologies require the use of purpose built hardware to hear and/or to see content. This approach attempts to ensure that only licensed users (those with the hardware) can access the content. In addition, it seeks to deny system users access to the secret decryption key.
However, although hardware based CP technologies can provide robust protection, it can be very difficult to build hardware that is sufficiently robust to protect a secret key against a sufficiently determined adversary. Moreover, once the secret key is known, building a version of the hardware that can be used to hear and/or see content can be relatively straightforward. Accordingly, conventional technologies can lack a level of protection that is sufficient to deter determined adversaries.